Techniques for parameter reporting of elements in an optical transmission system using high loss loopback (hllb) data and a line monitoring system implementing the same

ABSTRACT

A system and method consistent with the present disclosure provides for automated line monitoring system (LMS) baselining that enables capturing and updating of operational parameters specific to each repeater and associated undersea elements based on high loss loopback (HLLB) data. The captured operational parameters may then be utilized to satisfy queries targeting specific undersea elements in a Command-Response (CR) fashion. Therefore, command-response functionality may be achieved without the added cost, complexity and lifespan issues related to deploying undersea elements with on-board CR circuitry. As generally referred to herein, operational parameters include any parameter that may be derived directly or indirectly from HLLB data. Some example non-limiting examples of operational parameters include span gain loss, input power, output power, gain, and gain tilt.

TECHNICAL FIELD

The present application relates to communication systems and, moreparticularly, to a system and method for utilizing high loss loopback(HLLB) data to measure and report operating parameters of repeaters andother elements in an undersea fiber optic network.

BACKGROUND

Subsea fiber optical communications systems need routine monitoring toguarantee their performance and minimize potential loss of service bydetecting and solving wet plant faults and possibly aggressive threatsat an early stage. Currently established monitoring technologies includethe use of line monitoring systems (LMS) to detect signal peaks loopedback from each undersea repeater and terminal with high loss loopback(HLLB) technology.

When there is a change in performance along the optical path, theamplitudes of these loopback signals change in the repeaters surroundingthe fault location. The changes present distinct patterns which may beutilized to identify fault conditions. Such fault conditions include,for example, changes in fiber span loss, changes in optical amplifierpump laser output power, and fiber breaks. Some approaches torecognizing fault conditions based on a corresponding fault signatureinclude utilizing automatic signature analysis (ASA). Existing ASA-basedfault analysis can detect relatively large changes in the transmissionsystem, but often lack accuracy to report small changes that mayindicate degraded performance of a particular element over time.

Some undersea transmission systems utilize repeaters withCommand-Response (CR) features that allow for operational parameterssuch as output power and input power to be queried directly from eachrepeater. However, Command-Response requires specialized hardware withineach repeater that can significantly increase unit costs and reduceoperational lifespan, which is particularly problematic in an underseaenvironment that makes repairs impractical.

BRIEF DESCRIPTION OF THE DRAWINGS

Reference should be made to the following detailed description whichshould be read in conjunction with the following figures, wherein likenumerals represent like parts:

FIG. 1 is a simplified block diagram of one exemplary embodiment of asystem consistent with the present disclosure.

FIG. 2 simplified block diagram of another exemplary embodiment of asystem consistent with the present disclosure.

FIG. 3A is a simplified block diagram of line monitoring equipment (LME)system consistent with the present disclosure.

FIG. 3B shows an example workflow for the LME of FIG. 3A to performperiodic line monitoring, consistent with an embodiment of the presentdisclosure.

FIG. 4A is a graph showing differential gain data values for a pluralityof repeaters for an optical transmission system without a detected faultcondition, in accordance with an embodiment of the present disclosure.

FIG. 4B is another graph that shows differential gain data values thatcorrespond with a fault between repeaters of an optical transmissionsystem consistent with an embodiment of the present disclosure.

FIG. 5 is a graph that shows measured differential of differential loopgains (dDLG) mapped to a position coefficient from −1 to 1 andassociated weighting coefficients relative to terminal T1, in accordancewith an embodiment of the present disclosure.

FIGS. 6A to 6E show example fault signatures for fault conditions thatmay be detected by an LME consistent with the present disclosure.

FIG. 7 is a block diagram of one example automatic signature analysisprocess in accordance with an embodiment of the present disclosure.

FIG. 8 shows a plurality of fault signatures detected along atransmission system in accordance with an embodiment of the presentdisclosure.

FIGS. 9A and 9B show the plurality of fault signatures of FIG. 8decomposed into separate fault signatures, in accordance with anembodiment of the present disclosure.

FIG. 10 is a graph showing loop gain shifts after increasing the overalllength of an optical transmission system, in accordance with anembodiment of the present disclosure.

FIG. 11 shows an example amplifier pair of a repeater suitable for usein the optical transmission system of FIG. 1, in accordance with anembodiment of the present disclosure.

FIG. 12 shows one example reportable parameter table (RPT) in accordancewith an embodiment of the present disclosure.

FIG. 13 is a flow chart illustrating operations according to a methodconsistent with the present disclosure.

DETAILED DESCRIPTION

In general, a system and method consistent with the present disclosureprovides for automated line monitoring system (LMS) baselining thatenables capturing and updating of operational parameters specific toeach repeater and associated undersea elements based on high lossloopback (HLLB) data. The captured operational parameters may then beutilized to satisfy queries targeting specific undersea elements in aCommand-Response (CR) fashion. Therefore, command-response functionalitymay be achieved without the added cost, complexity and lifespan issuesrelated to deploying undersea elements with on-board CR circuitry. Asgenerally referred to herein, operational parameters include anyparameter that may be derived directly or indirectly from HLLB data.Some example, non-limiting examples of operational parameters includespan gain loss, input power, output power, gain, and gain tilt.

FIG. 1 is a simplified block diagram of one exemplary embodiment of WDMtransmission system 100 consistent with the present disclosure. Ingeneral, the system 100 may be configured to calculate a loop gain valueassociated with each repeater/amplifier using LMS signals sent from bothends of a bi-directional transmission path 102. Those of ordinary skillin the art will recognize that the system 100 has been depicted as ahighly simplified point-to-point system form for ease of explanation. Itis to be understood that a system and method consistent with the presentdisclosure may be incorporated into a wide variety of network componentsand configurations. The illustrated exemplary embodiments herein areprovided only by way of explanation, not of limitation.

As shown, the system 100 may include a first terminal T1 and secondterminal T2 coupled by two unidirectional optical paths 110, 120, whichtogether form the bi-directional optical transmission path 102. Thefirst terminal T1 is coupled to a first end of the transmission path 102and the second terminal T2 is coupled to a second end of thetransmission path 102. The term “coupled” as used herein refers to anyconnection, coupling, link or the like by which signals carried by onesystem element are imparted to the “coupled” element. Such “coupled”devices are not necessarily directly connected to one another and may beseparated by intermediate components or devices that may manipulate ormodify such signals.

The optical path 110 may carry optical data on a plurality of channels(or wavelengths) in one direction from a transmitter 112 in the terminalT1 to a receiver 114 in the terminal T2. The optical path 120 may carryoptical data on a plurality of channels (or wavelengths) in a directionopposite from the direction associated with path 110 from a transmitter124 in the terminal T2 to a receiver 122 in the terminal T1. Withrespect to terminal T1, the optical path 110 is an outbound path and theoptical path 120 is an inbound path. With respect to terminal T2, theoptical path 120 is an outbound path and the optical path 110 is aninbound path. The optical path 110 may include an alternatingconcatenation of optical fibers 116-1 to 116-n and optical amplifiers118-1 to 118-n, and the optical path 120 may include an alternatingconcatenation of optical fibers 126-1 to 126-n and optical amplifiers128-1 to 128-n.

The optical path pair (e.g., optical paths 110, 120) may include sets ofamplifier pairs 118-1 to 118-n and 128-1 to 128-n disposed withinhousings 131-1 to 131-n of associated repeaters R1 . . . Rn andconnected by pairs of optical fibers 116-1 to 116-n and 126-1 to 126-n.The pairs of optical fibers 116-1 to 116-n and 126-1 to 126-n may beincluded in an optical fiber cable together with fibers supportingadditional path pairs. Each repeater R1 . . . Rn may include a pair ofamplifiers 118-1 . . . 118-n and 128-1 . . . 128-n for each supportedpath pair. Optical amplifiers 118-1 . . . 118-n and 128-1 . . . 128-nare illustrated in simplified form may include one or more erbium dopedfiber amplifiers (EDFAs) or other rare earth doped fiber amplifiers,Raman amplifiers or semiconductor optical amplifiers. A HLLB path 132-1to 132-n may be coupled between optical paths 110, 120, for example, inone or more of the housings 131-1 to 131-n of the repeaters R1 . . . Rn,and may include, for example, one or more passive optical couplingcomponents, as will be described in greater detail below.

Line monitoring equipment (LME) 140, 142 may be located at both of theterminals T1, T2 to provide HLLB monitoring of the path pair 110, 120.The LME 140 may launch one or more LME test signals, e.g. at differentwavelengths and/or different frequencies, into one optical path 110(e.g., an outbound optical path). Each of the HLLB paths 132-1 to 132-nmay couple a sample of the LME test signals propagating in optical path110 into the forward propagating direction of the other optical path 120(e.g., an inbound optical path). The LME 140 may then receive andmeasure the samples to detect changes in loop gain as an indication of afault in the system. The received samples of the LME test signalsreceived through HLLB paths 132-1 to 132-n in response to LME testsignals are referred to herein as HLLB loopback data or simply loopbackdata.

The LME 142 may launch one or more LME test signals, e.g. at differentwavelengths and/or different frequencies, into one optical path 120(e.g., an outbound optical path). HLLB paths 132-1 to 132-n may couple asample of the LME test signals propagating in optical path 120 into theforward propagating direction of the other optical path 110 (e.g., aninbound optical path). The LME 142 may then receive and measure thesamples (loopback data) to detect changes in loop gain as an indicationof a fault in the system. A variety of transmitter and receiverconfigurations for the LME 140, 142 for transmitting LME test signalsand receiving and measuring loopback data are known.

A variety of HLLB path configurations useful in a system consistent withthe present disclosure are known. Also, although the each of therepeaters R1 . . . Rn is shown is shown as having an associated HLLBpath 132-1 to 132-n, the HLLB paths may be located in other locationsand/or may not be located in every repeater R1 . . . Rn. In someembodiments, the HLLB paths 132-1 to 132-n may be symmetric inoperation, i.e., the function that describes the percent of opticalpower at each wavelength transferred from path 110 to path 120 by a HLLBpath 132-1 is the same as the function that describes the percent ofoptical power at each wavelength transferred from path 120 to path 110by the HLLB path 132-1. Alternatively, one or more HLLB paths may not besymmetric and different HLLB paths may have different transferfunctions.

For example, each of the pairs of amplifiers 118-1 to 118-n and 128-1 to128-n include a pumping scheme to facilitate the process of detectingoptical performance changes in the monitored path. In this example, eachof the amplifier pairs may be configured with an asymmetric pumpingconfiguration whereby each amplifier in a given amplifier pair has anoutput power different than the other. The asymmetric pumping scheme maytherefore be utilized to assign a direction to a particular measuredchange, and to identify the particular element that may be associatedwith the change. For example, a single repeater may have two amplifiers,e.g., A1 and A2, to amplify signals in each direction. The twoamplifiers A1 and A2 may be pumped by two similarly-configured lasers,e.g., L1 and L2. In this example, A1 may be pumped by 50% L1 and 50% L2.A2 may also be pumped in a similar fashion by its respective lasers. Incontrast, asymmetrical pumping can include A1 being pumped by, forinstance, 40% L1 and 60% L2, although other ratios are within the scopeof this disclosure. Likewise, A2 may be pumped by 60% L1 and 40% L2.

FIG. 3A shows an example line monitoring system (LMS) 300 consistentwith an embodiment of the present disclosure. The LMS 300 may besuitable for use in the LME 140 and/or LME 142 of FIGS. 1 and 2. LMS 300is shown in a highly simplified manner for purposes of clarity and notlimitation. The LMS 300 may be implemented in hardware (e.g.,circuitry), software, or a combination thereof. In an embodiment, theLMS 300 may be implemented at least in part as a plurality ofinstructions that may be executed by a controller (not shown) to carryout the LMS processes, e.g., process 1300 of FIG. 13. A controller, asgenerally referred to herein, may be implemented as a processor (e.g.,x86 process), field programmable gate array (FPGA), anapplication-specific integrated circuit (ASIC), or any other suitableprocessing device/circuitry.

As shown, the LMS 300 includes an enhanced automatic signature analysis(eASA) processor 301, a reportable parameter table (RPT) updater 302, anRPT storage 303, a baseline manager component 304, and a high lossloopback (HLLB) storage 305. The RPT storage 303 and HLLB storage 305may be implemented in a volatile or non-volatile memory area. Note, thecomponents of LMS 300 may not be physically located in the same systemand may be distributed throughout the WDM transmission system 100. Forexample, the RPT storage 303 and HLLB storage 305 may be located atterminal stations T1 and T2, respectively. Accordingly, LMSs consistentwith the present disclosure may communicate with each other to sharedata and/or processing components depending on a desired configuration.

The LMS 300 may receive loopback data 308 (or LME loopback data 308) inthe form of one or more LMS high loss loopback (HLLB) data sets from atransmission path in response to LME test signal(s) propagated on thenetwork. Loopback data 308 may also be referred to as HLLB data sets orsimply HLLB data. The loopback data 308 may then be stored in a memorythat provides HLLB storage 305. As discussed in greater detail below,the eASA 301 can operate on differential HLLB data sets from multiplesystem endpoints (which may be referred to as terminal stations, orsimply stations) and from multiple measurement times to provide resultswith improved accuracy relative to ASA approaches that operate on asingle loopback data set. The eASA 301 may also detect changes near aterminal station/landing even when signatures of the same may beincomplete.

The RPT updater 302 (or RPT update model) may receive output from theeASA 301 and can map the output of the eASA 301 to operationalparameters corresponding to one or more associated repeaters/elements ofan optical transmission system, e.g., the WDM transmission system 100 ofFIG. 1. As discussed further below, the RPT updater 302 can comparebaseline RPT values to the values output by the eASA 301 to determinedeltas, which in turn may be used to calculate changes to operationalparameters. Thus, the RPT updater 302 may access RPT storage 303 tostore operational parameters and any updated RPT baseline values basedon the output of the eASA 301. One such example RPT table (or RPT lookuptable) that may be updated and stored in the RPT storage 303 is shown inFIG. 12. The RPT data of the RPT storage may also be referred to as acurrent baseline RPT.

The baseline manager 304 may be configured to provide HLLB baseline data(which may also be referred to as LME baseline data) to the eASA 301.The HLLB baseline data may include a current HLLB baseline stored in theHLLB storage 305. During operation, the baseline manager 304 maymaintain the current HLLB baseline data without modification, locallymodify the baseline data based on detected faults/conditions that exceeda first predefined threshold, or may replace an entire HLLB baselinedata set.

The baseline manager 304 may also be configured to provide/updatebaseline data stored in the RPT storage 303. During operation, thebaseline manager 304 may maintain the current RPT baseline data withoutmodification, locally modify the baseline data based on detectedfaults/conditions that exceed a first predefined threshold, or mayreplace an entire RPT baseline data set.

In an embodiment, the LMS 300 allows for periodic execution ofmonitoring and data reporting processes. During each monitoring cycle,the LMS 300 may receive new HLLB loopback data sets 308 from stations(e.g., based on LME test signals propagating along the WDM transmissionsystem 100 as discussed above with reference to FIG. 2), and thenperform automatic signature analysis on the received data sets using theeASA 301. The RPT updater 302 may then utilize the output of the eASA301 and the current HLLB baseline from the baseline manager 304 toupdate the RPT table values stored in the RPT storage 303. A user maythen query the LMS 300 in a command-response like fashion for monitoringresults such as input power, output power, gain, span loss, and tilt. Inturn, the LMS 300 may utilize the RPT data stored in the RPT storage 303to satisfy the requests.

One example workflow 350 for the LMS 300 is shown in FIG. 3B. As shown,at time (T) zero, the eASA 301 receives one or more HLLB data sets andcurrent HLLB baseline data from HLLB storage 305 as an input. Also atT=0, the RPT updater 302 receives RPT baseline data corresponding to theRPT table from RPT storage. The HLLB data sets may also be referred toas loopback data sets, and the HLLB baseline data may be referred to LMSbaseline data. Continuing on, the eASA 301 then analyzes the receivedHLLB data sets and compares to the same to the current HLLB baselinedata (HLLB_(current)) to determine one or more changes, e.g., based on afirst predefined threshold (e.g., 1%, %5, 10%, or other suitablethreshold). Any changes that exceed the first predefined threshold maybe stored/updated in the current HLLB baseline data (HLLB_(current)) ina memory to generate new HLLB baseline data (HLLB_(new)). The changesbetween the old HLLB baseline data (HLLB_(current)) and the receivedHLLB data sets may also be used to generate first RPT delta values(RPTΔ) for changing the operational parameters of the RPT table. Changesbetween the new HLLB baseline data (HLLB_(new)) and the old HLLBbaseline data (HLLB_(current)) may be used to generated changes for theRPT baseline data (RPTBaslineΔ). Before the changes are applied, a copyof the previous RPT baseline data may be stored in a memory(RPTBaseline_(old)). The new RPT baseline data may then be generated bysumming values of the prior RPT baseline data (RPTBaseline_(old)) withcorresponding values from the changed RPT baseline data (RPTBaslineΔ).Updated RPT parameters may then be calculated by summing the values ofthe previous RPT baseline data RPTBaseline_(old) with correspondingvalues from the first RPT delta values (RPTΔ).

The eASA 301 then updates the RPT baseline data and then stores the sameback into the RPT storage 303 to replace or otherwise adjust one or moreoperational parameters. Some such example operational parameters includeinput power, output power, gain, span loss, spectral tilt, and and/orspan length for each amplifier and adjacent span represented within theone or more received HLLB data sets.

Continuing on with FIG. 3B, after a predetermined period of time (e.g.,10 minutes, an hour, a day, a week) the LMS 300 may receive one or moreadditional HLLB data sets during a subsequent LMS cycle. The eASA 301may perform analysis on the HLLB data sets, and based on one or moremeasured operational parameters exceeding a predefined threshold, afault condition may be detected. In the event of a detected fault, thebaseline manager 304 may update one or more operational parameters inthe RPT storage 303 and HLLB baseline data sets in the HLLB storage 305.For instance, an amplifier with a degraded output power may be detectedby the eASA and an operational parameter value in the RPT tablecorresponding to the amplifier may be updated (see FIG. 12). Likewise,the HLLB baseline data may be updated to reflect the current operationalstatus of the amplifier. Thus, even those a re-baselining has occurredfor the loopback data, the RPT storage 303 can include an operationalparameter which may be representative of the fault or potential fault.

HLLB Data Set Collection and Analysis

As discussed above with reference to FIGS. 1 and 2, the WDM transmissionsystem 100 include high-loss loop-back optical paths in thebi-directional amplifier pairs in the undersea repeater bodies and inthe terminal amplifiers. For the following discussion and formulas, eachof the HLLB paths 132-1 to 132-n of FIG. 1 may be referenced using thenotation HLLBi,j, where i is the terminal and j is the loopback path.These optical paths route a small amount of light at specified testchannel wavelengths from the optical fiber in one direction oftransmission to the optical fiber in the reverse direction oftransmission. These reflected round trip signals are detected by the LMS300 in the terminal stations and converted or otherwise provided to theLMS 300 as loopback data 308.

This loopback data 308 can be measured for at least one opticalfrequency/wavelength within the transmission band of the optical path,and in some cases at two or more wavelengths. In one specific exampleembodiment, the high and low channel wavelengths (e.g., the minimum andmaximum wavelengths, respectively) for a given bandwidth may be selectedas the test signal channel wavelengths. Generation of the loopback data308 may include measurement from each terminal site, e.g., T1 and T2.Thus, loopback data 308 may include multiple HLLB data sets. In somecases, the loopback data 308 may include at least one or more of asingle data set for each branch fiber pairs, and two data sets fromtrunk fiber pairs, e.g., representing each direction of propagation. Inaddition, the loopback data 308 may include one or more data sets fromtarget portion(s) of the WDM transmission system when a specific portionof the transmission system is monitored. Note, for C+L fiber pairs, HLLBdata sets may be measured in both the C-band and L-band.

In an embodiment, accumulated noise along the transmission line that isrepresented within the loopback data 308 may be reduced or otherwiseminimized. To this end, differential loop gain may be given by:

DLG_(j)=HLLB_(T1,j)−HLLB_(T1,j−1)=HLLB_(T2,j−1)−HLLB_(T2,j)   Equation(1)

The differential loop gain shows the optical gain of the amplifiersbetween two repeaters, as discussed above with regard to FIGS. 1 and 2.The differential loop gain data may then be compared to baselinedifferential loop gain data stored in the HLLB storage 305 to detectfaults, as discussed above with regard to FIGS. 3A and 3B. Comparisonmay simply include subtracting the baseline's differential loop gaindata from the differential loop gain data resulting from Equation (1) toderive the differential of differential loop gain. The differential ofdifferential loop gain may therefore be given by:

dDLG_(j)=(DLG_(j))_(Data)(DLG_(j))_(Baseline)   Equation (2)

In scenarios where the WDM transmission system 100 is without fault, thedifferential of differential loop gain values fluctuates at about zero.For example, as shown in FIG. 4A, the differential loop gain data values404 are substantially zero. Note that the data points of FIG. 4A areshown after applying weighting to accommodate combining multi-site datasets, which is discussed in greater detail blow. For purposes ofproviding a non-limiting example, differential loop gain data valueshaving an absolute amplitude value of 0.25 or less may be consideredsubstantially zero, although other threshold values may be utilizeddepending on a desired level of sensitivity.

On the other hand, a fault condition may cause differential loop gaindata to have a unique signature, such as shown in FIG. 4B. In FIG. 4B, apump within an amplifier disposed between R3 and R5 may be degraded andresults in peak 405. The LMS 300 may include a plurality of predefinedsignatures to enable the eASA 301 to detect and classify associatederror conditions. Alternatively, or in addition to predefinedsignatures, the LMS 300 may be trained over time with signaturesprovided by trained technicians/plant managers.

Band gain delta (BDG) may be defined as the difference of dDLGs of highand low frequencies:

BGD_(j)=(dDLG_(j))_(LF)−(dDLG_(j))_(HF)   Equation (3)

Although differential loop gain minimizes or otherwise reduces theinfluence of noise in long distance transmission, the error rate of dataincreases relative to measurement distance. For transmission systemswith transmission path lengths of hundreds, thousands, or tens ofthousands of kilometers, the error accumulation may be significant. Inan embodiment, the introduction of error may be cancelled out bycombining the HLLB data from multiple terminals. For instance,measurements from LME 140 of T1 may be combined with measurements fromLME 142 of T2. The HLLB data from first and second terminal stations maytherefore be given by:

dDLG_(j) =r _(j)(dDLG_(j))_(T1)+(1−r _(j))(dDLG_(j))_(T2)   Equation (4)

where (dDLG_(j))_(T1) is differential of differential loop gain from T1,(dDLG_(j))_(T2) is differential of differential loop gain from T2 andr_(j) is the weighing factor of dDLG_(j) from T1.

Each HLLB loopback position may then be mapped to the positioncoefficient ranging between −1 and 1 (see FIG. 5) using the followingequation:

$\begin{matrix}{d = {\frac{2n}{N - 1} - 1}} & {{Equation}\mspace{14mu} (5)}\end{matrix}$

In an embodiment, a weighting factor may be applied to scale datadepending on the configuration of the system. The weighing factor may becalculated by:

$\begin{matrix}{r_{j} = {1 - \frac{1}{1 + {\exp \left( {- {aed}} \right)}}}} & {{Equation}\mspace{14mu} (6)}\end{matrix}$

where a is a scaling factor for the transmission system, and e is amathematical constant equal to 2.71828. Note, the weighing factor maychange based on a system configuration and the provided Equation (6) isnot intended to be limiting. For instance, a discrete array of numbersmay be utilized based on the particular configuration of the opticaltransmission system.

Also, a mid-span constant s may be defined, so that if r_(j) fallsoutside [s, 1−s] and the difference between (dDLG_(j))_(T1) and(dDLG_(j))_(T2) are too large, then:

max{|(dDLG_(j))_(T1)|, |(dDLG_(j))_(T2)|}>>min{|(dDLG_(j))_(T1)|,|(dDLG_(j))_(T2)|}  Equation (7)

Then r_(j) may be to be either 1 (if r_(j)>1−s) or 0 (if r_(j)<s), as isshown in FIG. 5.

In an embodiment, fault signature analysis may be performed by an LMS,e.g., LMS 300, to identify and localize one or more fault types fromHLLB data such as pump degradation, span loss, and so on. Such faultsignature analysis may be performed on multi-span fault signatures thatsurround a specific physical fault location.

As discussed above, predetermined fault signatures may be stored in amemory of the LMS for comparison purposes during processes performed bythe eASA 301, for example. The fault signatures may be based on, forinstance, simulations or may be generated (trained) based on measuredevents occurring on the WDM transmission system 100 during operation.Differential of differential loop gain data, which can be calculatedbased on the baseline HLLB data sets for each measurement frequency, mayalso be stored in a memory, e.g., in HLLB storage 305, of each LMS foruse during ASA analysis processes.

One example fault event/condition type the eASA 301 may detect includesdegradation of output power of an optical pump laser, which enables theoperation of optical amplifiers. The degradation may range from smalldecreases in output power to total failure of one or more pump lasers.Another example fault event type includes the degradation of fiber spanattenuation. Fiber span attenuation may range from small increases inattenuation to significant attenuation increase that may adverselyimpact optical performance through the span/segment in question.

One example ASA process flow 700 that may be performed by the eASA 301is shown in FIG. 7. During the process flow 700, a plurality ofdimensional digital filters, e.g., with respective shapes based on knownfault shapes for pump degradation, span loss, and so on, with the samelengths may be applied to the dDLG data resulting from Equation (4) andBGD data to offer preliminary results:

y1=filter(F1, dDLG_(HF))   Equation (8)

y4=filter(F4, dDLG_(HF))   Equation (9)

y5=filter(F5, dDLG_(HF))   Equation (10)

y3=filter(F3, dDLG_(HF))   Equation (11)

y2=filter(F2, BGD)   Equation (12)

where y is the signal processed by filter F(Fx,Dy), where Fx is theshape of curve and Dy is the input data. As shown above, shapes x=3, 4and 5 may correspond with pump degradation of laser L1, pump degradationof laser L2 and span loss. However, additional filters may be necessaryas dDLG can interact filters F3 and F4 at a same instance in time, forexample. In this case, it may not be possible to conclude as to whetherthe degradation is of laser L1 or laser L2. Thus, filter F2 isintroduced such that F2 and F3 together can predict pump degradation oflaser L1; F23 and F4 together can predict pump degradation of laser L2;and F2 and F5 can together predict span loss.

Continuing on, and in the event both the preliminary results of theprocessed dDLG data (y3, y4, y5) and the BGD data (y2) indicatesubstantially the same fault at substantially the same position (N), afault is then recorded at j. Assuming that the summation of theamplitudes of the y2 near position j is:

$\begin{matrix}{\xi = {\sum\limits_{i = {- 3}}^{2}\; {y\; 2\left( {j + i} \right)}}} & {{Equation}\mspace{14mu} (13)}\end{matrix}$

This disclosure has identified that this amplitude ξ can mapped to thevalue of the fault (δ) using:

δ=f(ξ)   Equation (14)

The function of y=f(x) can be fitted by varying the amplitude of thefault.

Turning to FIGS. 6A-6E, example fault condition signatures are shownconsistent with embodiments of the present disclosure. Span loss may becalculated by an LMS consistent with the present disclosure by dividingloss between two directions of propagation ranging from being entirelylocated in one of the two directions to being evenly divided between twodirections. For example, FIGS. 6C and 6D show two span losses at thesame position, with 6C showing loss in an inbound direction and FIG. 6Dis in an outbound direction, respectively.

In FIGS. 6C and 6D, the sub peaks 601-1 to 601-4 illustrate differenttrends. In particular, dDLG at positions 4 and 5 in FIG. 6D are up sincethe repeaters after the span will seek to recover the loss of the gain.On the other hand, dDLG at position 3 and 4 go up in the inbounddirection as shown in FIG. 6C. In the event span loss is a combinationof inbound span and outbound span, then the dDLG at position 3 andposition 5 will both go up. Therefore, span loss may be assigned to twodirections by a ratio of inbound span loss using the following equation:

$\begin{matrix}{r_{in} = \frac{1}{1 + {\exp \left( {- \frac{\delta}{Pm}} \right)}}} & {{Equation}\mspace{14mu} (15)}\end{matrix}$

where=y1(j−1)−y1(j+1), in this case j=4 and Pm is a function related toy1(N).

However, for a shore span loss such as shown in FIG. 6E, the initialdDLG data may be missing, so a shore span loss prediction functiony=p(x) may be used to estimate/predict the dDLG before the firstrepeater R1:

dDLG(0)=p(dDLG(1), dDLG(2))   Equation (16)

Therefore, Equation (16) may be used to calculate shore span loss andassign directions.

In some cases, multiple fault signatures corresponding to differentphysical locations along the WDM transmission system 100 may occur. TheeASA 301 may detect each individual fault signature and quantify aplurality of associated wet plant change events present along thetransmission path. In an embodiment, the fault signatures correspondingto the different fault events can be decomposed mathematically. Forinstance, as shown in FIG. 8, the peaks 801 and 802 may be isolated anddecomposed into separate and distinct signatures as shown in FIGS. 9Aand 9B, respectively. The isolated/decomposed signatures may then beindividually analyzed by the eASE 301 as discussed above.

In some scenarios, specific faults may be detected by an LMS withoutnecessarily performing automatic signature analysis on the HLLB data.For instance, HLLB data corresponding to a single amplifier pair may beutilized to detect a fiber break along the transmission path. Consider asituation in which a fiber is broken between repeater j−1 and repeaterj. As a result, HLLB data for the following/downstream repeaters afterrepeater j (or j−1) cannot be received. For example, in FIG. 2, a fiberbreak could occur between R3 and R4. Therefore, the LMS 140 in T1 maynot receive return signals from R4, R5, R6 and T2.

Similarly, T2 may not detect return signals from R3, R2, R1 and T1. Inthis case, the amplitudes of all missed peaks may be shown as apredefined value, e.g., −55 dB, in order to be displayed on the dataplots. For a system with two end terminals, the total number of missingpeaks in the HLLB data set from both ends should be greater than orequal to the total number of loopback paths, depending on whether thereis a single fiber break or multiple breaks at different physicallocations. For a system with one end terminals (e.g. branch), the totalnumber of missing peaks may appear more than two in a row. Thus, thefiber break fault condition and the location of the fault condition maybe detected based on the location and total number of the missing HLLBdata points.

The HLLB data corresponding to a single amplifier pair may also beutilized to detect failure of an optical filter within an HLLB path.Consider a case where there is a fiber break within the loopback path ofan amplifier pair at repeater j. In this case, the HLLB loopback signalsat all measurement frequencies from only that amplifier-pair will not bereceived and will be marked as −55 dB (or other predefined dB value).Unlike the fiber break in the transmission path, as discussed above, theloopback signals from all other downstream amplifier-pairs along theoptical path will still be received by an LMS. For example, in FIG. 2,with a loopback path break at repeater R3, the HLLB₃ will be marked as−55 dB. During subsequent processing, the eASA 301 may ignore/discardthe data point for HLLB₃. In any event, the optical filter faultcondition and the location of the fault condition may be detected basedon the location of the missing HLLB data points at a single repeater.

The HLLB data corresponding to a single amplifier pair may also beutilized to detect failure of an optical filter within a given HLLB path(see FIGS. 6A and 6B). In each direction of propagation along the WDMtransmission system 100, each HLLB path may include wavelength-selectiveoptical filters to select the optical frequencies that get reflected inthe opposite direction of propagation. In general, there are twomeasurement frequencies per optical band (e.g., C-band versus C+L),although more are possible and the particular number may beapplication-specific. In one specific example embodiment, at least twooptical frequencies per optical band are selected as measurementfrequencies. The selected measurement frequencies may correspond withthe respective edges of the spectrum band, e.g., high and lowwavelengths of the spectrum, although other embodiments are within thescope of this disclosure. Using two or more optical frequencies in thismanner may advantageously allow an LMS consistent with the presentdisclosure to measure spectrum tilt as discussed in greater detailbelow.

Continuing on, when one optical filter is broken, for example in theloopback path of the repeater R3 to T1 (FIG. 2), then the return signalto T1 at that measurement frequency (HLLB_(T1,3)) will be missing in thedata set, and thus DLG₃ and DLG₄ corresponding with R3 and R4,respectively, will be influenced. Optical filter faults within HLLBpaths may therefore be detected/inferred by identifying the missing datapoint. Note, DLG₃ may still be derived via measurement data from T2, asthe loopback path between R3 and T2 remains operational. In this case,DLG₃ may be given by:

DLG₃=HLLB_(T1,3)−HLLB_(T1,2)=HLLB_(T2,2)−HLLB_(T2,3)   Equation (17)

And thus, the missing HLLB_(T1,3) data point can be predicted/estimatedby:

HLLB_(T1,3)=HLLB_(T1,2)+HLLB_(T2,2)−HLLB_(T2,3)   Equation (18)

Thus, failure of an optical filter within a given HLLB path and thelocation of the fault condition may be detected based on the missingHLLB data points at only one repeater (and the fact that data points arepresent for one measurement frequency at the given repeater).

After the eASA 301 identifies the location and amplitudes of each of thechange events in the transmission path since the most-recentre-baselining in each physical location, the identified change eventsmay then be used to calculate updates in RPT data stored in the RPTstorage 303. The RPT data may include operational parameter values foreach amplifier and adjacent fiber span/segment in a monitored fiberpair. The calculated changes from the eASA 301 may then be used toadjust RPT reference data within the RPT table to produce new absolutevalues for each operational parameter (See FIG. 12). Therefore,operational parameters associated with each monitored amplifier/span maybe individually reported on without direct communication with theelements via the optical transmission path. This may advantageouslyallow for relatively simple wet plant devices and may avoid additionaltraffic being introduced onto the same.

As shown in FIG. 12, with additional reference to FIG. 11, theoperational parameters reportable by an LMS consistent with the presentdisclosure may include, for example, input power, output power and gain,and/or amplifier accumulated gain tilt. To provide the reportableparameters, the LMS can use HLLB data to detect pump power and span losschanges, amplitude, and direction, and then use those changes tocalculate changes operational parameter values based on an amplifiermodel. The amplifier model may be used, in a general sense, to derivevalues that quantify the relationship between reportable operationalparameters and a fault in the system. For instance, consider theoutbound direction (e.g., upper half) of repeater N in FIG. 11. Inputpower change can be calculated based at least in part by the outputpower change of repeater N−1 minus the span loss change between therepeater N and N−1 in the outbound direction. Output power change can becalculated based at least in part by input power change summed with theoptical gain change. Thus, gain changes may then be calculated via theamplifier model based on the determined change of pump laser(s).

In an embodiment, the RPT updater 302 performs an RPT update processbased on the most-recent ASA results output by the eASA 301 and theloopback data 308. In this embodiment, the RPT update process utilizesan amplifier model provided for each amplifier pair. The RPT updateprocess also utilizes an initial input set of RPT values for allparameters and all monitored amplifier pairs which may be provided by afield technician during deployment or during staging, for instance.

In an embodiment, the amplifier model may be used to calculate thechange in amplifier output power in response to a detected decrease inpump laser power, and to calculate the change in amplifier output powerin response to a detected increase in fiber span insertion loss andcorresponding reduction in amplifier input power. The relation betweenamplifier input power, output power and gain, and the span loss of theadjacent fiber span can be given by:

P _(out,i) =P _(in,i) +G _(i)   Equation (19)

P _(in,i+1) =P _(out,i) −S _(i,i+1)   Equation (20)

where P_(out,i) is the output power of repeater Ri, P_(in,i) is theinput power of repeater Ri, G_(i) is the gain of repeater Ri, S_(i,i+1)is the span loss between repeater Ri and repeater Ri+1.

A decrease in amplifier laser pump results in a decrease in output powerand gain, G, for the affected amplifier, and a decrease in input powerand increase in gain for the following/subsequent down-stream amplifier.The accumulated gain tilt of both amplifiers are affected, but withopposite amplitude, so that there is little accumulated impact on thetilt of downstream amplifiers.

An increase in fiber span insertion loss (S), results in a decrease inthe input power of the adjacent amplifier and possibly the next-adjacentamplifier, and an increase in G in both amplifiers. The accumulated gaintilt of both amplifiers and all downstream amplifiers are affected.

The change in round-trip gain shape can be inferred from changes in therelative peak height of the HLLB peaks on either extreme of the fiberpair spectrum band as follows:

ΔTilt_(i)=dDLG_(i,HF)−dDLG_(i,LF)   Equation (21)

where the dDLG_(i,HF) is the high frequency differential of differentialloop gain at repeater R_(i), and the dDLG_(i,LF) is the low frequencydifferential of differential loop gain at repeater Ri.

However, the distribution of this change in gain shape between the twodirections of propagation can be more difficult to measure. The detectedchanges in round trip tilt may be assigned to a propagation directionbased on the directionality of the detected span loss and pump powerchange events from the ASA process 700 above. For example, if a spanloss increase occurs only in one direction of propagation, then anychange in detected gain tilt is assigned to that direction ofpropagation. When multiple faults (N) appear simultaneously, the dDLGmay be decomposed into N parts (e.g., see FIGS. 8, 9A and 9B) and eachcorresponds to one single fault. Then the tilt can be calculatedindividually and added up to form a collective tilt.

Returning to FIG. 3A, an overall LMS process, e.g., generally depictedas a work flow in FIG. 3B, may perform a Baseline Manager process toensure that new HLLB data sets are analyzed by the ASA. The BaselineManager process may also maintain synchronization between the baselinedata sets for both the ASA analysis of HLLB data and the RPT update ofcurrent RPT values based on previously determined RPT values.

In some cases, configurable threshold values may be provided todetermine the amplitude of ASA or RPT update results that will triggerthe overall process to execute either localized or global updating ofthe RPT and HLLB baseline data sets. In general, updating the baselinedata sets for LMS comparisons allows new faults to be detected nearexisting faults without the ASA analysis being impaired by the presenceof overlapping fault signatures. Thus, baseline data sets may be updatedon specific repeater span(s) adjacent an event that caused thefaults/changes, which in turn avoids re-baselining the entire system inorder to allow for other parts of the network to be monitored relativeto their previous/earlier values. For example, in some cases six (6)data points may be used for fault shape detection, and those 6 pointsnear an event may each be updated so that the influence of a currentfault will be minimized or otherwise reduced. However, other amounts ofdata points may be utilized and the provided example is not intended tobe limiting.

In some cases, the RPT and HLLB baseline data sets may not be updatedbased on relatively minor/small change events. Detection accuracy can bebetter for larger faults, so continuing to monitor total fault amplitudeas a fault continues to grow may be advantageous instead of continuouslyupdating the baseline and then continuously monitoring small changes infault amplitude. For example, it is beneficial to monitor a span losschange that is slowly growing from 1 dB to 3 dB, instead of constantlyre-baselining when the fault increases by 1 dB. Also, there is lessaccumulation of detection inaccuracy when the RPT update results of eachLMS cycle are based on the reference RPT values and the current ASAresults, instead of the cycle-by-cycle accumulation of inaccuracy whenthe results of each cycle are added to the results of the previouscycle.

Consider a scenario wherein a first fault in the system of FIG. 2exceeds the threshold for localized baseline updating, but a secondfault does not. The first fault will be incorporated in the HLLBbaseline data by injecting the change of HLLB caused by fault(ΔHLLB_(i,j)) into the baseline so that the next run will only show thesecond fault, as is shown in FIG. 9. In this example, the DLGcorresponding to the fault that does not exceed the threshold may be setto zero/nulled and the DLG having the fault that exceeds the thresholdmay be kept. Thus, the change of HLLB baseline data may then be given:

$\begin{matrix}\left\{ \begin{matrix}{{{DLG}_{j} + {\Delta \; {HLLB}_{{T\; 1},{j - 1}}}} = {\Delta \; {HLLB}_{{T\; 1},j}}} \\{{\Delta \; {HLLB}_{{T\; 1},{T\; 1}}} = 0} \\{{{DLG}_{j} + {\Delta \; {HLLB}_{{T\; 2},j}}} = {\Delta \; {HLLB}_{{T\; 2},{j - 1}}}} \\{{\Delta \; {HLLB}_{{T\; 2},{T\; 2}}} = 0}\end{matrix} \right. & {{Equation}\mspace{14mu} (22)}\end{matrix}$

The newly generated HLLB baseline (HLLB_(i,j))_(new) can be calculatedfrom the old HLLB baseline (HLLB_(i,j))_(old) by:

(HLLB_(i,j))_(new)=(HLLB_(i,j))_(old)+ΔHLLB_(i,j)   Equation (23)

After repair, a fiber may be inserted into the original system to shiftthe peaks, as is shown in FIG. 10. An LMS consistent with the presentdisclosure may then update the distance change automatically using thereceived loopback data 308. If the distance data is different from twoends, an averaged value may be used.

FIG. 13 is a flow chart illustrating one exemplary embodiment 1300 of afault detection process that may be performed by an LMS consistent withthe present disclosure. Exemplary details of the operations shown inFIG. 13 are discussed above. As shown, the method 1300 includestransmitting 1302 line monitoring equipment (LME) test signal(s) on thetransmission path from one or more terminal stations. The method 1300may then receive 1304 loopback data in the form of HLLB data sets(HLLB_(i,j)) from the transmission path in response to the LME testsignal(s).

The method 1300 may then generate 105 differential loop gain dataDLG_(j−j−1) based on the received HLLB data sets HLLB_(i,j) usingEquation(1) The method 1300 may then generate 1306 differential ofdifferential loop gain data sets (dDLG_(j.)) by subtracting loopgainvalues in each DLG_(j) data set with values in a corresponding loopgainvalue baseline dataset using Equation (2), for example. Additionalpreprocessing in act 1306 may further include applying error reductionto each dDLG_(j) using Equation (4), and weighting and mapping of loopgain values based on Equations (5)-(7).

The method 1300 may then identify 1308 one or more fault types and faultamplitudes based on ASA analysis. One example process 700 for ASAanalysis is discussed above with regard to FIG. 7, which will not berepeated for brevity. The method 1300 may then update 1310 a reportableparamters table (RPT) based on identified changes, e.g., input powerchanges, output power changes, gain, tilt, and so on, for each of therepaters and associated elements represented within the dDLG_(j) data.The method 1300 may then include comparing 1312 updated data in the RPTtable to the current baseline RPT. In response to one or moreoperational parameters exceeding a predefined threshold, sending areporting message to a user or other monitoring process. The reportingmessage may comrpise, for instance, one or more of an identifier of arepeater, an identifier of an operational parameter, and/or anoperational parameter value.

In accordance with an aspect of the present disclosure an opticalcommunication system is disclosed. The optical communication systemcomprising an optical transmission path, a plurality of repeaterscoupled to the optical transmission path, each of the repeaterscomprising a high loss loopback (HLLB) path, first line monitoringequipment (LME) coupled to the first end of the transmission path, thefirst LME being configured to transmit first LME test signals on theoptical transmission path and receive first LME loopback data from theoptical transmission path in response to the LME test signals, the firstLME loopback data comprising a peak associated with the location of eachof the HLLB paths on the transmission path, a controller coupled to thefirst LME, the controller to generate a plurality of operationalparameters based on the first LME loopback data, each of the operationalparameters corresponding to a repeater of the plurality of repeaters,select one or more repeaters of the plurality of repeaters, and send areporting message to a remote computer, the reporting message includinga representation of one or more operational parameters of the pluralityof operational parameters associated with each of the selectedrepeaters.

In accordance with another aspect of the present disclosure a method ofmonitoring an optical transmission path in an optical communicationsystem is disclosed. The optical transmission path including a pluralityof repeaters coupled to the transmission path, each of the repeaterscomprising a high loss loopback (HLLB) path, and the method comprisingtransmitting a first line monitoring equipment (LME) test signal on thetransmission path, receiving first LME loopback data from thetransmission path in response to the first LME test signal, the firstLME loopback data having peaks associated with a location of each of theHLLB paths on the transmission path, storing LME baseline data in amemory based on the first LME loopback data, and sending a reportingmessage to a user, the reporting message including at least oneoperational parameter associated with a repeater of the plurality ofrepeaters based on the stored LME baseline data.

The foregoing description of example embodiments has been presented forthe purposes of illustration and description. It is not intended to beexhaustive or to limit the present disclosure to the precise formsdisclosed. Many modifications and variations are possible in light ofthis disclosure. It is intended that the scope of the present disclosurebe limited not by this detailed description, but rather by the claimsappended hereto.

Embodiments of the methods described herein may be implemented using acontroller, processor and/or other programmable device. To that end, themethods described herein may be implemented on a tangible,non-transitory computer readable medium having instructions storedthereon that when executed by one or more processors perform themethods. Thus, for example, the LMS 300 may include a storage medium tostore instructions (in, for example, firmware or software) to performthe operations described herein. The storage medium may include any typeof tangible medium, for example, any type of disk including floppydisks, optical disks, compact disk read-only memories (CD-ROMs), compactdisk rewritables (CD-RWs), and magneto-optical disks, semiconductordevices such as read-only memories (ROMs), random access memories (RAMs)such as dynamic and static RAMs, erasable programmable read-onlymemories (EPROMs), electrically erasable programmable read-only memories(EEPROMs), flash memories, magnetic or optical cards, or any type ofmedia suitable for storing electronic instructions.

It will be appreciated by those skilled in the art that any blockdiagrams herein represent conceptual views of illustrative circuitryembodying the principles of the disclosure. Similarly, it will beappreciated that any block diagrams, flow charts, flow diagrams, statetransition diagrams, pseudocode, and the like represent variousprocesses which may be substantially represented in computer readablemedium and so executed by a computer or processor, whether or not suchcomputer or processor is explicitly shown. Software modules, or simplymodules which are implied to be software, may be represented herein asany combination of flowchart elements or other elements indicatingperformance of process steps and/or textual description. Such modulesmay be executed by hardware that is expressly or implicitly shown.

The functions of the various elements shown in the figures, includingany functional blocks labeled as “processor”, may be provided throughthe use of dedicated hardware as well as hardware capable of executingsoftware in association with appropriate software. The functions may beprovided by a single dedicated processor, by a single shared processor,or by a plurality of individual processors, some of which may be shared.Moreover, explicit use of the term “processor” should not be construedto refer exclusively to hardware capable of executing software, and mayimplicitly include, without limitation, digital signal processor (DSP)hardware, network processor, application specific integrated circuit(ASIC), field programmable gate array (FPGA), read-only memory (ROM) forstoring software, random access memory (RAM), and non-volatile storage.Other hardware, conventional and/or custom, may also be included.

Unless otherwise stated, use of the word “substantially” may beconstrued to include a precise relationship, condition, arrangement,orientation, and/or other characteristic, and deviations thereof asunderstood by one of ordinary skill in the art, to the extent that suchdeviations do not materially affect the disclosed methods and systems.Throughout the entirety of the present disclosure, use of the articles“a” and/or “an” and/or “the” to modify a noun may be understood to beused for convenience and to include one, or more than one, of themodified noun, unless otherwise specifically stated. The terms“comprising”, “including” and “having” are intended to be inclusive andmean that there may be additional elements other than the listedelements.

Although the methods and systems have been described relative to aspecific embodiment thereof, they are not so limited. Obviously, manymodifications and variations may become apparent in light of the aboveteachings. Many additional changes in the details, materials, andarrangement of parts, herein described and illustrated, may be made bythose skilled in the art.

What is claimed is:
 1. An optical communication system comprising: anoptical transmission path; a plurality of repeaters coupled to theoptical transmission path, each of the plurality of repeaters comprisinga high loss loopback (HLLB) path; first line monitoring equipment (LME)coupled to a first end of the transmission path, the first LME beingconfigured to transmit first LME test signals on the opticaltransmission path and receive a first LME loopback data from the opticaltransmission path in response to the first LME test signals, the firstLME loopback data comprising a peak associated with a location of eachof the HLLB paths on the transmission path; a controller coupled to thefirst LME, the controller to: generate a plurality of operationalparameters based on the first LME loopback data, each of the operationalparameters corresponding to a repeater of the plurality of repeaters,wherein each of the plurality of operational parameters are stored in alookup table in a memory, the lookup table associating each of theplurality of repeaters with corresponding operational parameters; selectone or more repeaters of the plurality of repeaters; and send areporting message to a remote computer, the reporting message includinga representation of one or more operational parameters of the pluralityof operational parameters associated with each of the selectedrepeaters.
 2. The optical communication system of claim 1, wherein eachof the plurality of operational parameters comprise at least one of anoutput power value, a gain value, and/or amplifier accumulated gain tiltvalue.
 3. (canceled)
 4. The optical communication system of claim 1,wherein the reporting message is sent in response to the controllerreceiving a Command-Response (CR) message from a user.
 5. The opticalcommunication system of claim 4, wherein the CR message includes atleast one repeater identifier, and wherein each of the selected one ormore repeaters of the plurality of repeaters correspond with the atleast one repeater identifier.
 6. The optical communication system ofclaim 1, the controller further to: store the first LME loopback data asa current baseline loopback data in a memory; receive a second LMEloopback data in response to second LME test signals being transmittedon the transmission path by the first LME; compare the received secondLME loopback data to the current baseline loopback data to identify achange of at least a first operational parameter and an associatedrepeater of the plurality of repeaters; and update an operationalparameter of the plurality of operational parameters corresponding withthe associated repeater based on the identified change.
 7. The opticalcommunication system of claim 6, wherein the updated operationalparameter is updated based on an output of an amplifier model.
 8. Theoptical communication system of claim 6, wherein the controller isfurther to send an alert message to a user based on the updatedoperational parameter exceeding a predefined threshold.
 9. The opticalcommunication system of claim 6, further comprising an automaticsignature analysis (ASA) processor, and wherein the identified change ofthe first operational parameter is identified based at least in part onanalysis of at least the first LME loopback data by the ASA processor.10. The optical communication system of claim 1, wherein the first LMEtest signals comprise a plurality of channel wavelengths, the pluralityof channel wavelengths including a low value corresponding to a minimumchannel wavelength of a bandwidth associated with the opticaltransmission path, and a high value corresponding with a maximum channelwavelength of the bandwidth associated with the optical transmissionpath.
 11. The optical communication system of claim 1, wherein each ofthe plurality of repeaters include at least first and second amplifiersto propagate optical signals in a first and a second direction,respectively, and wherein the first and second amplifiers implement anasymmetrical pumping configuration whereby output power in the firstdirection is different from output power in the second direction. 12.The optical communication system of claim 1, further comprising: asecond LME coupled to a second end of the transmission path, the secondLME being configured to transmit second LME test signals on thetransmission path and receive a second LME loopback data from thetransmission path in response to the second LME test signal, the secondLME loopback data comprising a peak associated with the location of eachof the HLLB paths on the transmission path; and wherein the plurality ofoperational parameters are generated based on the first LME loopbackdata and the second LME loopback data.
 13. A method of monitoring anoptical transmission path in an optical communication system, theoptical transmission path including a plurality of repeaters coupled tothe transmission path, each of the repeaters comprising a high lossloopback (HLLB) path, the method comprising: transmitting a first linemonitoring equipment (LME) test signal on the transmission path;receiving a first LME loopback data from the transmission path inresponse to the first LME test signal, the first LME loopback datahaving peaks associated with a location of each of the HLLB paths on thetransmission path; storing a LME baseline data in a memory based on thefirst LME loopback data; sending a reporting message to a user, thereporting message including at least one operational parameterassociated with a repeater of the plurality of repeaters based on thestored LME baseline data; and transmitting a second LME test signal onthe transmission path; and receiving a second LME loopback data from thetransmission path in response to the second LME test signal, the secondLME loopback data having peaks associated with the location of each ofthe HLLB paths on the transmission path, wherein the LME baseline datastored in the memory is based on the received first and second LMEloopback data.
 14. (canceled)
 15. The method of claim 13, wherein theoperational parameter comprises at least one of an output power value, again value, and/or amplifier accumulated gain tilt value.
 16. The methodof claim 13, wherein the report message is sent in response to receivinga request message from the user, the request message including anidentifier of at least one repeater of the plurality of repeaters. 17.The method of claim 13, the method further comprising: storing aplurality of operational parameters in a memory, the plurality ofoperational parameters based on the received first LME loopback data;receiving the second LME loopback data in response to second LME testsignals being transmitted on the transmission path by the first LME;comparing the received second LME loopback data to the stored loopbackdata to identify a change in at least a first operational parameter andan associated repeater of the plurality of repeaters; and in response tothe identified change exceeding a first predefined threshold, updatingan operational parameter of the plurality of operational parameterscorresponding with the associated repeater based on the identifiedchange.